1.

A red LED emits light at 0.1 watt uniformly around it. The amplitude of the electric field of the light at a distance of 1 m from the diode is :

Answer»

1.73 V/m
2.45 V/m
5.48 V/m
7.75 V/m

Solution :INTENSITY`1=P/(4pir^2)` But i`=1/2in_0E_0""^2C`
`:. I=1/2in_0E_0^2xxC`
So `E_0=P/(4pir^2)=1/2in_0E_0^2xxC`
`E_0^2=(2P)/(4piin_0r^2C)=(2xx0.1xx9xx10^9)/(1xx3xx10^8)`
`E_0=sqrt6 =2.45` V/m.


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